Brooding Chickens Killed, How Long do I have?

Opossum found its way in to kill my two brooding chickens. The eggs have been laid on for about 10 days or so. The eggs could have been without hen between 6 and 30 hours. How long can an egg that far along go without a hen? I have transferred them to an incubator now, but wanted to see if there is hope for this batch of 24 eggs. THANKS!

PS. Temp never got lower than 50 degrees, and this morning when I found the issue, it was 60 degrees.
ALSO, I cracked open a few of the eggs that I thought might not be salvageable and found that the chicks were about an inch long with all appendages including beak clearly developed (very very small though). About how much longer should it take from this point to have them hatch. I read that I have to turn the eggs every 5 hours...is that correct? My incubator has a fan for even heat. Thanks for the help everyone!

If only six hours you have a good chance, I have had broodies return to the wrong nest, leaving thier eggs uncovered for 1/2 of the day and still had a good hatch, but agree with above if its 80 degrees out they can go longer unattended then if its 30 degrees out.